Field of the Invention
The present invention relates to a sheet feeding apparatus which feeds a sheet in an image forming apparatus to a sheet conveying path when an image is formed, and an image reading apparatus equipped with the sheet feeding apparatus, and the image forming apparatus.
Herein, examples of the image forming apparatus include an electrophotographic copying machine which forms an image in a recording medium using an electrophotographic image forming system, an electrophotographic printer (for example, a laser beam printer, and an LED printer), and a facsimile apparatus.
Description of the Related Art
As a sheet feeding apparatus equipped in an image forming apparatus, there is a configuration of a so-called manual tray system in which a tray is provided in a side surface of the apparatus and the sheet on the tray is fed besides a configuration of feeding a sheet from a sheet storage portion provided in the apparatus.
The sheet feeding apparatus of the manual tray system is configured such that a pickup roller abuts on the sheet on the tray and the sheet is fed to a sheet conveying path while the pickup roller rotates at the time of feeding the sheet. There are various methods of making the pickup roller abut on the sheet according to applications and specifications. For example, there is a method of making the sheet-stacked tray move toward the pickup roller so as to abut on each other, or a method of making the pickup roller supported to a lifting and lowering plate move toward the sheet according to the movement of the lifting and lowering plate so as to abut on each other.
Herein, when the sheet feeding apparatus performs a feeding operation, a collision noise is generated when the pickup roller abuts on the sheet. On the other hand, in recent years, there is a request for damping the noise when the image forming apparatus is operated. Therefore, a countermeasure for the suppression of the collision noise generated when the pickup roller comes in conflict with the sheet is essential particularly for the sheet feeding apparatus of the manual tray system which is generally provided in a side surface of the apparatus.
Therefore, there is proposed a method of suppressing such a collision noise in the related art. For example, Japanese Patent Laid-Open No. 2011-131949 discloses a sheet feeding apparatus in which the sheet-stacked tray goes up by rotation control of a cam and a biasing force of a spring so as to make the sheet on the tray abut on the pickup roller, and a convex portion which comes in contact with the cam when the tray goes up is provided in the tray. Then, a going-up speed when the tray goes up is restricted by a friction force generated when the cam and the convex portion of the tray come in contact with each other, so that the collision noise between the pickup roller and the sheet is attenuated.
In recent years, from the viewpoint of space saving and cost reduction, a one-way clutch which allows only one-directional rotation is frequently used as a drive configuration of the sheet feeding apparatus. Herein, in a case where the one-way clutch is provided in a driving force transfer portion which transfers a driving force of a drive source such as a motor to the cam of the configuration disclosed in Japanese Patent Laid-Open No. 2011-131949, a load in the one-directional rotation is lightened by the characteristics of the one-way clutch. Therefore, when the biasing force of the spring is large, the cam and a rotation shaft supporting the cam rotate in the light load direction by the biasing force of the spring. For this reason, the cam receives both rotation driving forces, that is, a driving force transferred from the drive source and a driving force based on the biasing force of the spring. Therefore, the driving force causing the cam to rotate becomes large, and the pickup roller comes into strong conflict with the sheet, thereby generating a loud collision noise.